The present invention relates to a wheel mounting assembly for mounting a wheel of a motor vehicle on the hub or brake drum of the vehicle and has particular application for the mounting of wheels to large trucks which carry freight.
In vehicles having demountable wheels, the most common type of fastening means for the wheels includes a series of threaded members such as studs or bolts fixed to the brake drum or hubs on the vehicles. For purposes of illustration, FIG. 1 is included herewith to show this fastening means. This figure is an elevational view with parts broken away showing the conventional mounting assembly. Bolts or studs "B" are arranged in a circle concentric with the axis of the drum or hub "C". An inner vehicle wheel "D" and an outer vehicle wheel "E" are provided with a series of countersunk holes "F" for receiving the studs or bolts. In the most common type of wheel mount in use today, the countersunk holes "F" are doubly beveled. The wheel is placed on the studs when the wheel is to be secured in place. Next a centering device "G", which consists of a partially hollow nut assembly having threads on the inside to be received by the stud and having threads on the outside to receive the wheel nut, is then screwed on the stud. This centering device "G" has an integral nut "H" formed at one end thereof and at the other end thereof has a doubly beveled portion "I" extending outwardly from the device. The bevel surface furthest from the nut "H" engages the outer bevel surface of the stud receiving hole "F" of the inner wheel "D". As this centering nut assembly is screwed onto the stud, the beveled portion of the centering device engages the corresponding beveled portion of the stud receiving holes of the wheel and centers the wheel on the studs. Once the threaded centering assembly has been screwed tight on the stud, the second wheel assembly is mounted over the centering nut. The other beveled surface of the centering nut engages the inner beveled surface of the stud receiving hole in the outer wheel to center the outer wheel on the studs. Next a wheel nut "J" is then threaded onto the centering device to secure the second wheel to the hub. This wheel nut "J" has a beveled surface which engages the outer bevel surface of the outer wheel. When this nut is screwed tightly in place, the wheels are centered and securely held to the hub.
A major disadvantage of this type of assembly for securing the dual wheels to the hub include the problem that the centering device "G" is held away from the hub "C". Thus the weight of the vehicle load is transmitted to the wheels from a position on the stud spaced from the hub as shown in FIG. 1. This arrangement causes severe shearing stresses on the studs and in fact it is not unusual for these studs to shear, causing a dangerous situation for drivers or bystanders when the truck is moving down a highway at high speeds under heavy loads. This problem in the past has caused tremendous expense for truck operators in maintaining vehicles having this type of wheel mounting structure.
Secondly, by having the bevel of the centering device being the device for transmitting the load of the truck to the wheel, there is tremendous pressures placed on these beveled surfaces. These pressures have caused breakage of the wheels themselves. The wheels crack and shear from these pressures, again causing extensive maintenance problems for truck operators.
This has long been a recognized problem in the United States. In some foreign countries such as in Europe, it has been the practice to increase the diameter of the lug size or decrease the diameter of the wheel holes so that the wheels more closely fit on the studs of the wheel to minimize this problem. Further, a spring washer has been used between the outer wheel and the wheel nut to minimize shearing forces on the beveled surfaces of the stud receiving holes in the wheels. This has reduced the problem to such an extent that some manufacturers in the United States have been going to this system for mounting wheels to hubs. However, at the present time, a great majority of the trucks on the road today use the older system described above, which has the associated problems also discussed above. With these trucks, it is believed to be too expensive to convert the older trucks to the new design.
The present invention is directed to a retrofitting device to be used with the older stud and wheel design to make the wheel mounting assembly a much safer and economical assembly than has heretofore been possible and specifically to overcome the problems described above.